Pavement Design TTP Orientation Seminar 2011
What are Pavements? Engineered structures in contact with the earth's surface built to facilitate movement of people and goods Pedestrians Personal vehicles Freight and freight handling Trains and trams Aircraft and spacecraft
Pavement Types Asphalt Concrete Surface Granular bases Subgrade Concrete Surface Various bases Subgrade Surface Treatment Thin sprayed asphalt on granular bases Permeable Pavement Open graded asphalt or concrete layers, open granular layers, on uncompacted subgrade
What are Pavements?
What are pavements?
What are pavements?
Why Build Pavements? Provide all-weather mobility for road users
Why Build Pavements?
Why Build Pavements?
Why Build Pavements?
Who are the Stakeholders? User Owner Builder Society Internal External
Pavement Anatomy Natural Ground Level (NGL) PAVED ROAD UNPAVED ROAD Cut Shoulder Surfacing Base Wearing Course Subbase Selected Layers Surface Drain Subgrade In situ material Fill Pavement Layers Material Depth Subsurface Drain
Pavement Life Cycle Infrastructure Life Cycle Deployment Maintenance Rehabilitation Reconstruction (Abandonment? Reuse?) Goal at all stages is greater efficiency how is efficiency defined?
Where Are We Now? Years Infrastructure Pavement Research 1948-1980 Deployment Materials, Design, Cost Allocation 1970-2050 Management M & R Scheduling, Condition Assessment
Years Infrastructure Pavement Research 1995-2025 Reconstruction Reconstruction, Materials Optimization, Traffic Considerations, ReDesign 2010-2050 Sustainability Materials ReUse, Vehicle/Pavement Interaction, New Materials, Information Technology Integration
Is There a Pattern? Continued expansion of the system boundaries in which pavement problems are defined Materials Pavement Pavement Network Sustainable Transportation Infrastructure System Transportation Facility Network
Traffic What Causes Pavement Environment Distress? Interaction of traffic/environment, construction quality, materials, design
California: 1912 the good old days? Australia: 1914
Traffic Variables Highways - it s the trucks Loads Tire pressures Speeds Dynamics (interaction with roughness) Which are most important? One fully loaded truck pass causes same damage as about 5,000 passes of an SUV
Traffic Measurement of traffic counts load measurements Prediction of future traffic growth factors for vehicle repetitions will load limits change on highways? are your loads controlled?
Big Truck - 1960
Big Truck - 2001
Super Single Tires
Australian for truck Road Train
Local Government Pavement Design Some agencies Standard cross sections and materials Little or no construction inspection (particularly compaction) No money for testing and analysis Other agencies Design for particular traffic, environment, soils Good construction inspection Testing and analysis (is there a net cost savings?) Standard specifications and design methods Greenbook (mostly in S. California) Use of state specifications (much of N. California, joint powers financing, federally funded projects) Use of consultants
What are Pavements Made Of? and will this change? Most pavements are made of engineered soils and processed rock Asphalt concrete is 85% aggregate by volume; 10% asphalt; some plastic, rubber modifiers Portland cement concrete is 70% aggregate by volume; 11% portland cement; up to 25% of cement replaced by fly ash; some steel Nearly all of these materials can be perpetually recyclable into the same infrastructure
Pavements: will the demand for them increase or decrease? Pavements sorted by transportation mode Streets, roads, highways, freeways, parking Railroads, switching yards, intermodal yards Runways, taxiways, aprons Land-side port facilities, container yards Bike paths, sidewalks, other hardscape
What is the impact on pavements of efforts to improve sustainability? Vehicle fuel economy and fuel type will change Fuel type change impact on available materials? Fuel economy change impact on functional and structural requirements? Smoothness requirements Impacts on product life cycle and waste Pneumatic tire loads and inflation pressures Operating speeds and suspension systems Repetitions
How can the environmental impact of pavements be reduced? Understand the pavement life cycle Identify environmental costs Consider environmental costs in decisionmaking Identify how to reduce environmental costs considering interactions with other systems Determine how to make new methods standard practice
Some basic good practices Minimize the annual use of new materials Perpetual reuse Make materials/pavements last longer Thinner pavements Reduce the environmental costs of new materials and recycling Local materials Reduce energy needs Low-impact materials Reduce the delay associated with construction
Caltrans Funded UCPRC Research Sustainability Issues: Nonrenewable fuel depletion Greenhouse gas emissions Global climate change Local air quality Projects: Modified Binders Deep In Situ Recycling Foamed asphalt Pulverization Warm Mix Asphalt
Deep In-Situ Recycling New AC Overlay Cracked AC repeated overlays Recycled Layer grind Granular layers Subgrade Remaining Granular Subgrade Currently developing project selection, mix design and construction guidelines
New pulverization and in-place stabilization equipment
Warm mix asphalt Additives to asphalt concrete reduce temperature for effective compaction of asphalt concrete Advantages: Better compaction in cold weather Reduced energy costs May reduce emissions Possible disadvantages: May increase risk of rutting, moisture damage
Asphalt paving with conventional mix
Same project with Warm Mix Asphalt
Caltrans Funded UCPRC Research Sustainability Issues: Congestion Low mobility Fatalities and injuries Projects: CA4PRS Faster construction from innovative scheduling; Shorter closures Less traffic delay Fewer accidents
Los Angeles Basin Freeway Network Santa Monica San Fernando Valley 405 Los Angeles 710 Ports of LA, Long Beach 5 10 60 Orange County San Bernardino 215 Riverside concrete pavements to be rebuilt 2000-2015 project lengths 2 to 50 km
I-710 Traffic Detour Plan - Simulation Boundary
Simulation Before Construction
I-710 Reduction of Pavement Thickness Using Mechanistic Design Conventional design 535 mm thick asphalt concrete 8 % air-voids, same mix design throughout Mechanistic design 75 mm PBA-6a 125 mm, 5 % air-voids, AR-8000 75 mm, Rich Bottom
CA4PRS: Case Study on I-15 Devore Reconstruction Project
Construction Scenario One Roadbed Continuous (24/7) 72-Hour Weekday Continuous 55-Hour Weekend Continuous 10-Hour Night-time Closures Schedule Comparison Total Closures Closure Hours Cost Comparison ($M) User Delay Agency Cost Total Cost Max. Peak Delay (Min) 2 400 5.0 15.0 20.0 80 8 512 5.0 16.0 21.0 50 10 550 10.0 17.0 27.0 80 220 2,200 7.0 21.0 28.0 30
Caltrans Funded UCPRC Research Sustainability Issues: Life Cycle Analysis Projects: Long-life pavement design Comparison of life cycle environmental costs for 20, 40 and 100 year pavement design lives using PaLATE
CO 2 Payback Period Using Life Cycle Analysis Savings are not immediately realized Payback ~30-45 years in the future Future is highly uncertain Technological advancements Uncertain demand What s the right analysis period? Break-even point